We engineer an Aluminum (Al)-based plasmonic device coated with TiO2 and SiO2 layers for biosensing applications. First, the thicknesses of TiO2, SiO2, and Al layers are optimized under the angle interrogation scheme for a wavelength of 1550 nm. Over an optimized value of TiO2, SiO2, and Al film thickness, the variation trend in the performance parameters is studied for a range of thicknesses of 2D nanomaterials for the biofunctionalization of the sensing surface. Later, with the optimized intermediate layers, we present a comparative analysis of Al-based Kretschmann configuration with Graphene, MoS2, MXene, and Fluorinated Graphene. It is observed that the TiO2-SiO2-Al-Fluorinated Graphene-based plasmonic device provides enhanced sensing parameters (sensitivity =120°/RIU, Figure of Merit = 430 RIU-1).
Aluminum-Graphene based plasmonic sensor has been proposed for bio-sensing applications and analyzed for the resonant angle interrogation in the communication band. The addition of the graphene layer above a thin Aluminum metal layer, separated by a high index dielectric Silicon layer is considered. The performance parameters such as sensitivity, reflectivity-amplitude, and figure of merit are analyzed and compared with the conventional plasmonic sensors for the wavelength of 1550 nm. The combination of graphene and silicon layer leads to stronger interactions with biomolecules along with improved sensitivity. The simulated results show that the increase in the number of graphene layers helps to further increase the sensitivity of the biosensor. The maximum sensitivity observed for the plasmonic device was found to be 131°/RIU at the wavelength of 1550 nm.
Periodic plasmonic nanostructures on a thin homogeneous metal layer are used to excite surface plasmons (SPs) for normal incident light in the optical communication band. The structures are engineered using rigorous coupled-wave analysis by considering sensitivity, linewidth, and reflection amplitude as the evaluation parameters. The presence of SP mode at the thin metal–substrate interface in the proposed plasmonic device adds a self-reference capability while capturing the minute refractive index and thickness variations. The wavelength shift in SP mode at the nanostructure–analyte interface is used to measure the changes in the refractive index of the analyte, and the number of waveguide modes is used to capture the changes in the thickness of the analyte. The proposed engineered plasmonic nanostructures offer a sensitivity of 1100 nm/refractive index unit and a resonance line width of 18 nm while taking into account the fabrication constraints. The proposed structures are further simulated for the detection of hemoglobin concentration (using its refractive index measurement) in human blood in the optical communication band (1450 to 1520 nm). The normal incident action eases the integration of engineered plasmonic substrate with optical fibers that can be used both to excite SP and to interrogate the spectral reflectance.
A plasmonic device with a self-referenced capability that uses periodic nanostructures has been proposed and analyzed in terms of the spectral response. Aluminum-based periodic nanostructures that scatter incoming radiation towards a thin homogeneous metal layer, are used to excite Surface Plasmons (SP) for normal incident light. The rigorous coupled wave analysis method is used to engineer the periodic nanostructures and evaluation of performance parameters. The sensitivity, figure of merit and reflective amplitude are considered as the main parameters for engineering the device. The electromagnetic field simulations reveal the presence of waveguide mode and two plasmonic modes, namely, SP mode and substrate mode with three different interactions in the device. The shift in SP mode is used to detect the minute changes in the refractive index of the analyte and the number of exciting waveguide modes is used to capture the changes in the thickness of the analyte. The presence of substrate mode adds the self-reference capability to the proposed plasmonic device due to the independence of any change in the refractive index and thickness of the analyte. The proposed device has been engineered to offer a competitive sensitivity of 1000 nm/RIU and figure of merit 300 RIU-1 with the fabrication constraints taken into account. Since the proposed structures work under normal incidence conditions which makes this design integrable to the end of an optical fiber that can be used both to excite SP and to interrogate the spectral reflectance.
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